Re: [RFC Disable suspend on a specific device] This is a little change in linux power scheme

[Michael Trimarchi <trimarchi@gandalf.sssup.it>]

Hi,

Rafael J. Wysocki wrote:
> On Tuesday 07 April 2009, Michael Trimarchi wrote:
>   
>> This is a little rework of linux power scheme. TODO:
>> - remove recursive call
>> - clean-up code
>>
>> Avoid suspend of a device that is connected with other coprocessor
>> like GSM chip.
>>     
>
> Well, can you please tell us a bit about the motivation for this work?
>
> I don't like the approach, but I'd like to know what you're trying to achieve.
>   
I works on an hardware that have the gsm connect to wm8753 and the 
bluetooth subsystem
too direct connected. So I would like that a phone call for example 
remains on during
system suspend. With this approch I can disable suspend of an entire 
subtree of device,
that can be used by other hardware component. This change avoid any 
specific change to the
driver.

Michael
> Rafael
>
>
>   
>> Signed-off-by: Michael Trimarchi <trimarchi@gandalf.sssup.it>
>>
>> ---
>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>> index 3098c46..2a6ddb3 100644
>> --- a/drivers/base/power/main.c
>> +++ b/drivers/base/power/main.c
>> @@ -63,6 +63,40 @@ void device_pm_unlock(void)
>>  	mutex_unlock(&dpm_list_mtx);
>>  }
>>  
>> +int device_set_may_suspend_enable(struct device *dev, void *data)
>> +{
>> +	/* if the device is suspend the subtree is in may_suspend status */
>> +	if (!dev->power.can_suspend)
>> +		goto out;
>> +
>> +	dev->power.may_suspend = (unsigned int)data;
>> +	device_for_each_child(dev, data,
>> +			      device_set_may_suspend_enable);
>> +out:
>> +	return 0;
>> +}
>> +
>> +/**
>> + *	device_set_suspend_enable - enable/disable device to suspend
>> + */
>> +int device_set_suspend_enable(struct device *dev, int enable)
>> +{
>> +	mutex_lock(&dpm_list_mtx);
>> +
>> +	if (dev->power.can_suspend == !!enable)
>> +		goto out;
>> +
>> +	/* Update device children to avoid suspend */
>> +	device_for_each_child(dev, (void *)!!enable,
>> +			      device_set_may_suspend_enable);
>> +
>> +	dev->power.can_suspend = !!enable;
>> +out:
>> +	mutex_unlock(&dpm_list_mtx);
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(device_set_suspend_enable);
>> +
>>  /**
>>   *	device_pm_add - add a device to the list of active devices
>>   *	@dev:	Device to be added to the list
>> @@ -77,6 +111,13 @@ void device_pm_add(struct device *dev)
>>  		if (dev->parent->power.status >= DPM_SUSPENDING)
>>  			dev_warn(dev, "parent %s should not be sleeping\n",
>>  				 dev_name(dev->parent));
>> +		if (!device_can_suspend(dev->parent)) {
>> +			mutex_unlock(&dpm_list_mtx);
>> +			/* if the parent has suspend disable, propagate it
>> +			 * to the new child */
>> +			device_set_may_suspend_enable(dev, 0);
>> +			mutex_lock(&dpm_list_mtx);
>> +		}
>>  	} else if (transition_started) {
>>  		/*
>>  		 * We refuse to register parentless devices while a PM
>> @@ -120,13 +161,13 @@ static int pm_op(struct device *dev, struct dev_pm_ops *ops,
>>  	switch (state.event) {
>>  #ifdef CONFIG_SUSPEND
>>  	case PM_EVENT_SUSPEND:
>> -		if (ops->suspend) {
>> +		if (device_can_suspend(dev) && ops->suspend) {
>>  			error = ops->suspend(dev);
>>  			suspend_report_result(ops->suspend, error);
>>  		}
>>  		break;
>>  	case PM_EVENT_RESUME:
>> -		if (ops->resume) {
>> +		if (device_can_suspend(dev) && ops->resume) {
>>  			error = ops->resume(dev);
>>  			suspend_report_result(ops->resume, error);
>>  		}
>> diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
>> index 41f51fa..1197b13 100644
>> --- a/drivers/base/power/power.h
>> +++ b/drivers/base/power/power.h
>> @@ -1,6 +1,13 @@
>>  static inline void device_pm_init(struct device *dev)
>>  {
>>  	dev->power.status = DPM_ON;
>> +	dev->power.can_suspend = 1;
>> +	dev->power.may_suspend = 1;
>> +}
>> +
>> +static inline int device_can_suspend(struct device *dev)
>> +{
>> +	return (dev->power.can_suspend && dev->power.may_suspend);
>>  }
>>  
>>  #ifdef CONFIG_PM_SLEEP
>> diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
>> index 596aeec..25236aa 100644
>> --- a/drivers/base/power/sysfs.c
>> +++ b/drivers/base/power/sysfs.c
>> @@ -43,6 +43,34 @@
>>  static const char enabled[] = "enabled";
>>  static const char disabled[] = "disabled";
>>  
>> +static ssize_t suspend_show(struct device *dev, struct device_attribute *attr,
>> +				char *buf)
>> +{
>> +	return sprintf(buf, "%s\n", device_can_suspend(dev)
>> +		? enabled : disabled);
>> +}
>> +
>> +static ssize_t
>> +suspend_store(struct device *dev, struct device_attribute *attr,
>> +		const char *buf, size_t n)
>> +{
>> +	char *cp;
>> +	int len = n;
>> +
>> +	cp = memchr(buf, '\n', n);
>> +	if (cp)
>> +		len = cp - buf;
>> +	if (len == sizeof enabled - 1
>> +			&& strncmp(buf, enabled, sizeof enabled - 1) == 0)
>> +		device_set_suspend_enable(dev, 1);
>> +	else if (len == sizeof disabled - 1
>> +			&& strncmp(buf, disabled, sizeof disabled - 1) == 0)
>> +		device_set_suspend_enable(dev, 0);
>> +	else
>> +		return -EINVAL;
>> +	return n;
>> +}
>> +
>>  static ssize_t
>>  wake_show(struct device * dev, struct device_attribute *attr, char * buf)
>>  {
>> @@ -76,10 +104,11 @@ wake_store(struct device * dev, struct device_attribute *attr,
>>  }
>>  
>>  static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
>> -
>> +static DEVICE_ATTR(suspend, 0644, suspend_show, suspend_store);
>>  
>>  static struct attribute * power_attrs[] = {
>>  	&dev_attr_wakeup.attr,
>> +	&dev_attr_suspend.attr,
>>  	NULL,
>>  };
>>  static struct attribute_group pm_attr_group = {
>> diff --git a/include/linux/device.h b/include/linux/device.h
>> index fdb073b..dc9f242 100644
>> --- a/include/linux/device.h
>> +++ b/include/linux/device.h
>> @@ -487,6 +487,7 @@ extern struct device *device_find_child(struct device *dev, void *data,
>>  				int (*match)(struct device *dev, void *data));
>>  extern int device_rename(struct device *dev, char *new_name);
>>  extern int device_move(struct device *dev, struct device *new_parent);
>> +extern int device_set_suspend_enable(struct device *dev, int enable);
>>  
>>  /*
>>   * Root device objects for grouping under /sys/devices
>> diff --git a/include/linux/pm.h b/include/linux/pm.h
>> index de2e0a8..7586a90 100644
>> --- a/include/linux/pm.h
>> +++ b/include/linux/pm.h
>> @@ -319,6 +319,9 @@ struct dev_pm_info {
>>  	pm_message_t		power_state;
>>  	unsigned		can_wakeup:1;
>>  	unsigned		should_wakeup:1;
>> +	unsigned		can_suspend:1;
>> +	unsigned		may_suspend:1;
>> +
>>  	enum dpm_state		status;		/* Owned by the PM core */
>>  #ifdef	CONFIG_PM_SLEEP
>>  	struct list_head	entry;
>>     
>
>